The invention relates to a method for operating an electric circuit arrangement which has a low-voltage sub-network and a high-voltage sub-network, which are operatively connected to one another particularly by a coupling device. A test signal is transmitted from one of the sub-networks to the other sub-network in order to detect a fault depending on the reception of the signal in the other sub-network and to switch the circuit arrangement to a safe state.
The invention further relates to a device for operating an electric circuit arrangement which has a low-side voltage sub-network and a high-side voltage sub-network, which are operatively connected to one another particularly by a coupling device. The device comprises a safety device which transmits a test signal from one of the sub-networks to the other sub-network in order to detect a fault depending on the reception of the signal in the other sub-network and to switch the circuit arrangement to a safe state.
The invention further relates to a circuit arrangement comprising a corresponding device.
Methods for operating electric circuit arrangements as well as corresponding circuit arrangements are basically known from the prior art. Such circuit arrangements are particularly used in the so-called hybrid vehicles or respectively vehicles comprising a hybrid drive device. In so doing, a low-voltage sub-network is provided as the on-board electrical system of the vehicle and a high-voltage sub-network as a component of the drive means. Because a significantly higher electrical power is required for the drive than for the on-board electrical system of the vehicle, the two sub-networks have a different voltage level, whereby the one is denoted as the low-voltage sub-network and the other as the high-voltage sub-network. Because the two sub-networks are basically electrically isolated from one another, said sub-networks are generally connected to one another via a coupling device, which overcomes an insulation barrier between said two sub-networks, in order, for example, to supply the low-voltage sub-network with energy from the high-voltage sub-network. In order to reliably detect sources of faults, for example, in order to be able to ensure that the power output stages of the circuit arrangement are switched into a safe state when the driver switches off the drive device, software-independent switch-off paths have to be provided. It is known to date to conduct a signal, which is separate and independent of a low-voltage control unit and a high-voltage control unit, from the low-voltage sub-network to the high-voltage sub-network or respectively from the low-voltage unit to the high-voltage unit. An interruption of the signal at any location on the signal path is then detected as a source of the fault and the circuit arrangement as a whole is transferred into a safe state. Up until now, a separate transmission channel was additionally used to overcome the isolation barrier.